I believe the theory you're referring to is what Wikipedia calls the theory of Abiogenic petroleum origin [1]. But that theory is for hydrocarbon liquids and ga

I believe the theory you're referring to is what Wikipedia calls the theory of Abiogenic petroleum origin [1]. But that theory is for hydrocarbon liquids and gasses, not for coal. The two theories can be complementary, i.e. coal and peat from buried plant matter and (some or all) oil from planetary upwelling (and perhaps from 'deep microbes'). I'm not taking a position here myself although I do find the theory interesting, particularly the theory of a deep microbial biota. I think you're right that it is generally discounted in the mainstream scientific community. [1] https://en.wikipedia.org/wiki/Abiogenic_petroleum_origin https://en.wikipedia.org/wiki/Abiogenic_petroleum_origin